We are currently working to determine whether optogenetic stimulation of various brain structures can activate the mesolimbic dopamine system, using fiber photometry. We found that stimulation of supramammillary glutamateric neurons, medial septal glutamateric neurons, or anteromedial thalamic neurons reinforces behavioral responses. We are testing the hypotheses that the stimulation of these structures can activate the mesolimbic dopamine system. We are obtaining data that are consistent with the hypotheses.